This invention relates to a projectile which is provided with a propellant charge and a base nozzle from which, after firing the projectile from a weapon tube, hot propellant charge gases exit during the flight. A sealing disc is arranged in the base nozzle for providing a seal against environmental effects while the projectile is in storage.
Projectiles of the above type may be "base-bleed" projectiles having a gas generator to reduce base suction or post-accelerated projectiles with rocket drives, referred to as rocket assisted projectiles (RAP). A post-accelerated projectile is disclosed, for example, in Handbook on Weaponry, second English Edition, 1982, page 535, FIG. 1119 (published by Rheinmetall GmbH, Dusseldorf). To attain a greater range, the tail section of such projectiles contains propellant charge which is ignited when the projectile is fired, for example, from a large-caliber weapon, such as a 155 mm or 203 mm gun. Due to the escape of the hot propellant charge gases through the base nozzle, the desired aerodynamic effect is imparted to the projectile, that is, the projectile is post-accelerated during flight and the total resistance is reduced.
To seal such projectiles against environmental influences such as humidity, dust and others, the nozzle openings in the base nozzle of such projectiles are conventionally closed or sealed. For this purpose, for example, threaded plugs made of metal or plastic or pressed-in plugs are used. It is a disadvantage of such plugs that they must be removed manually before the projectile is loaded into the weapon. Also, thin covering sheets made of metal, paper or plastic are known. A sheet metal cover foil disclosed in German Patent Document 3,248,014, preferably provided with predetermined break locations, is, upon firing of the projectile, caused to burst from the outside inwardly into the nozzle openings by the high gas pressure of the propellant gases during the acceleration phase in the gun barrel, thus permitting ignition of the propellant charge base-bleed assembly disposed in the tail section of the projectile.
Such a covering disc whose thickness should be between about 0.5 and 1.0 mm, and which must have an upstanding rim, can be fastened to the projectile by welding, soldering or by clamping by means of a sleeve nut, which are all labor-intensive operations.
Such thin and rigid foils are very sensitive to mechanical stresses, such as pressure or shock, and thus they tend to tear when the projectile is being handled (reloading, transporting) and are therefore no longer able to perform their function of protecting the projectile against environmental influences. Moreover, risks are high that parts of the metal cover disc will bend back into and firmly settle in the nozzle opening after firing and disadvantageously change the diameter of the nozzle opening.